We propose to conduct an explanatory open study of cyclical intravenous pamidronate administration in children with moderate to severe Osteogenesis Imperfecta (OI) to test the hypotheses that pamidronate will 1) significantly increase bone mass 2) reduce chronic bone pain 3) reduce the overall level of disability and 4) reduce disease activity assessed biochemically and histomorphometrically. This protocol was written by Dr. Francis Glorieux from the Shriners' Hospital for Children in Canada and is being conducted at this center with permission. The principal outcome measures to be assessed will be: 1) lumber spine and femoral neck bone mineral content and bone mineral density. 2) fracture rate and pain. 3) biochemical parameters of bone formation/resorption. 4) bone histomorphometry. 5) disability evaluation. 6) evidence of restoration of vertebral morphometry. One child with severe OI has entered the protocol.